Filter attachments on existing respirator masks, while providing an air-tight seal, suffer from various shortcomings related to ease-of use. Some types of attachments must be carefully oriented at a precise angle to initiate installation. Other types require careful orientation and multiple turns, or precise placement and strenuous stretching.
Replaceable respirator filter cartridges are required to allow installation of the filter to the mask without the use of additional tools. Existing respirators have numerous methods of filter attachment requiring use of the hands only (no tools), and which provide a robust airtight seal once the filter is attached. Three of the commonly used attachment methods are threaded, bayonet, and flexible flange. The existing threaded types require correct orientation to align the threads to begin engagement, followed by multiple rotations to fully attach the filter.
The existing bayonet types require precise alignment of the male and female elements of the connection, followed by ¼ turn to fully attach the filter. Bayonet connections are commonly shown to be confusing to orient at the precise correct angle to initiate installation, particularly for inexperienced users.
The flexible flange types have an elastomeric element which must be manipulated (bent and/or stretched) in a precise manner in conjunction with the filter, sometimes with considerable strength, to effect the attachment of the filter to the mask.